This invention relates in general to structural building blocks and, more specifically, to blocks having greatly improved thermal insulating properties while retaining structural integrity in the event of a fire.
Building blocks made from concrete or the like have long been used in construction of walls, buildings, etc. Generally the blocks are rectangular in shape, with parallel vertical faces and vertical open cells therethrough. Blocks can be assembled with layers of mortar between adjacent surfaces, or the blocks may incorporate various keying arrangements which allow mortarless construction. Generally, once a wall or portion thereof is assembled, at least some of the open cells are filled with concrete with steel reinforcing rods running through the concrete in the cells. Such walls are sturdy, long lasting and generally economical to erect. However, the thermal insulating characteristics of such walls is rather low and wasteful of energy in heating or cooling a building using such walls.
Insulating panels are often added on one or both sides of block walls to increase insulating efficiency. Such additions, while often effective, add to wall thickness, are costly in materials and erection time and sometimes fail due to poor bonding, differential thermal expansion, etc.
Attempts have been made to incorporate foam or fibrous insulation material into the blocks themselves. For example, the block cells may be filled with an insulating foam. However, the block webs between cells still act as thermal energy bridges, so that the foam filled blocks are only slightly more efficient than air filled cells. Also, building codes often require that many cells be filled with concrete and reinforcing rods, reducing the erfectiveness of the few remaining foam filled cells.
Foam sleeves or inserts are available from Korfil incorporated in a "U"--shape which cover three walls of a block cell. These allow the center of the cell to be filled with reinforcing material. While showing some improvement in block insulating characteristics, these inserts do not overcome the problem of block webs acting as thermal bridges.
Attempts have been made to laminate or sandwich foam sheets between thin concrete blocks to make standard blocks. While these overcome the thermal bridging problem, they require a number of additional manufacturing steps beyond those for a standard block. Laminated blocks tend to have low strength and may suffer failures at the glue bond line. Also, in the event of fire, many foam material easily melt or burn, destroying the structural integrity of the block which may result in failure of the wall.
Thus, there is a continuing need for improved building blocks which have improved thermal insulating qualities, are simple and inexpensive to construct and assemble and have high strength and structural integrity, even when exposed to high heat or fires.